Apparatus for measuring charts



v Sept.7,1943. H. B. WEBSTER 2 2,328,762

APPARATUS FOR MEASURING CHARTS Filed Oct. 27, 1941 //v l EN TOR H11 11bwcbster A condition responsive apparatus arenotsuscepsivellcharacteristics.

Patented Sept. 7, 1943 v 2,328,762 o rr aa'rns iron MEASURING onaars righ' In. W bster; Oakland, Calif.,

Standard Oil T'Company of California,

assignor to San Fralicisico, Galitl, incorporation of; De aware entrainoetob rzv, 1941, Serial No; 416,735

1 This invention relates to an apparatus "for measuring linear distanceson a chart orthe like on which is'traced a reoord 01' marking of avariable. quantity, such as pressure cornpared with time, andparticularly refers toa device for measuring distances on charts frompressure recorders for deep wells, such as those offltlie Marx PatentNo. 1,955,855.

Charts which are utilizedby certain types of tible of previouscalibration so that theycannot be pr nt d r' uled ef ehand andfiafterthe record ismacle, have thc ilr numerical value read d yr y nerpolation ghetween the uled lines. Certain-typeset pressure responsivein- 1 struments that are used in deepiwells, for exarne ple that ofthet-lVlarxtPatent Noi 1,955,855, may be made with interchangeablesprings so. that a given'linear distance given on-the chart'with onespring has no relation toithe sa inear: distance with asp ineof differenforce expr sses srem v his easo such chart are'usuallysoaled lay-means.of a steel rule or like whichis laid upon the 'face or the chart-Ltdmeasure linear distances between certain parts of the record, thesedistances being compared with tabular values of displaemerit'andpressure. -,Pressure recordin -den f v this type usually prduce a char err cord i h a' on i uous y moving lateral timebase'isprovidedby means of clockwork, and the pressure .v'aluesf are,displaced lon itu l cameras. or ba l ne in a S ries of steps producedbyLthe-pressure responsiveelem nt of e reco de w ich may e a spingrestrained pistonor the like. The distance be- 3 tween the varioussteps andjthebaseline IBPI'G-r senting zeroor atrncsphericpressure is afunction oi the force responsivecharacteristic or the spring andpis-ton,if one is,used, and gives a measure of the pressures to which the deviceh iS'been sub: jected at the times indicated by the lateral displacementof the record Y I c This invention comprehends broadly a means forholding such a stripchart in a-predeterrnined position, in combinatiqn,with "a cursor, which y e ay e b maenlfi rfm a e alone an. accuratelythreadedrod or shaft, the latter being geared to a a revolutionindicate-r 1 counter vso calibrated that motion of the cursor across thechart between predetermined markings thereon may be translated throughrotation of the shaft I and operation of the revolution counter to givea direct reading on the dials oi the latter to a high degree ofaccuracy.

It is an object of this convem l0 i j ings on a chart and provided witha cursor which units the, linear distances Another object is to providea deviceoi this type in which the means for maintaining the chart inpredetermined relationship to the cursor and shaft are adjustableangularly as well'as. longitudinally.

,7 Anotherobject is to provide a gearedm'ea'surJ ing' device that may bereadily aligned with markcan be rapidlyJmoved to other linearly spacedmarkings onthe same chart, in combination with a means for indicatingdirectly in predetermined; between said markings; These and otherobjects and advantages of this. invention will be further apparent fronithe following description and iromthe drawing which illustrates apreferred embodiment of-this" invention.

111 the drawing, Figure 1 isfa plan view of this device with a chart inposition to be measured,

Figure Z is .a front elevational view of the device shown in Figure 1;

Figure 3 is an enlarged transverse verticalseetional View on lineIII-III of Figure 2. ,f a a r Figure 4 is an enlarged detail transversewe; tical sectional view on line Iv -Ivor" Figure 2;

By referring to the drawing and particularly to Figure 1, referencenumeral 19 represents a flat base, preferably of a hard material, suchas metal or synthetic plastic. At oneside oflbaseflil is the chartholder generally designated l l which is pivoted at l2 to have a slightdegree of angular motion. At the opposite end of chart. holder-H is anangular adjustment screw" Itsecured to post I l and engaging a threadedboss l5 at the opposite end of chart holder H from its pivoted supportl2. Each end of chart holder I5 is provided with a clamping bar I6andthreaded nuts H so that the chart l8 may be placed beneath bars 16and securely] clarrip'edto the holder H. Chart It! may be of paper orthin metal and is generally marked with a base line [9 representing zeroor atmospheric pressure. The record on the chart is generally ina'series of steps 20, 2}, 22, 23, 'etc., each one representing thepressure conditionin a certain depth in a well, for example, oralcertain condition of operation of a well. Because of the varying forcecharacteristics "of the, springsused in these-pressure recorders, it isnot feasible to' calibrate thechart previous to itsus with lines'representing pressure valuesandfspaced by pre determined intervals fromthe base line l9. Thus invention to provide a 55 the problem is tomeasure or scalethe distances ently operable means for measuring linear;distances on flat strip charts of the type produced; by pressurerecorder for use in deep wells;

, will not positively upward reactive. force against 31.

convert them by means of the spring calibration chart into pressurevalues.

In the example shown, the cursor 24 which is adapted to be moved acrossthe face of chart Hi to measure the linear distances between base lineH! and steps 20, 2|, 22, 23, etc. is illustrated as being displacedslightly below-base line It.

Cursor 24 is preferably but not necessarily made of a transparentmaterial, such as the methyl methacrylate polymer Lucite, and isprovided across its bottomface with a transverse index line 25 which maybe aligned with base line l9 or with'steps 20, 2|, 22, 23, etc. on chart8.

The upper surface of cursor 24 may be made convex to give a desireddegree of magnifica diameters of gears and 3! and the internal gearingof revolution counter 32,1 according to well known mathematicalprinciples, the figures shown on the dials 33 of revolution counterSZmay be made to read in inches, tenths, and thousandths or any otherdesired linear orarbitrary units. Preferably revolutionjcouhter 32 is ofthe reset, type provided with a wing nut 34 so that the dials 33 may bereset to zero at any time. I Also it is quite desirable that .revolution counter 32 is adapted to add in one direction and subtract intheother direction of rotation of its shaft.

It is desirable that carriage gitudinally with regard to withoutrotating the latter. Inthis example carriage 26 (Figure 3) is preferablymade in two parts, th upper part having a member 35"thre'ad-' ed at 36to engage the threads. on shaft 21. The lower part3! of carriage Z6 isprovided with a smoother unthreaded semi-circular groove 38 whichwillalign carriage 2a with shaft 21'but v engage the threads on thelatter. :Parts 35 and 37 of carriage 25 are ali ned or pinned togetherby means of four screws. 39 which are slidably received in upper member35. and are threadedly Resilient means, such as fiatsprings 46, areProvided above upper member-35 and the headset screws 39 so thattheupper memberwill normally be urged downwardly against threaded shaft 21to engage the latter.

In order selectively to releasecarriage. 26 from its threaded engagementwith shaft 21, a pair of cams 4! are supported by a transverse shaft 4extending through lower member til and provided with a knob 43 (Figure'3), so arranged that, when knob- 43 is rotated, cams M will en age thelower face of upper member 35 on each side of shaft 21 to lift member 35out of engagement with the threads of shaft 2?. Lower member 3'! is'keptin contact with shaft 2'! by means of, pins '44 (Figure 4) which areurged downwardly by means of springs 45 to engage base I 0 and exert anThis construction permits the operator to release the One end of shaft2115 provided 26 be movablelbnthreadedv shaft 2? engaged in lower member37.

' ressed in the desired units on dials 33.

This invention has been found to be much more 2,828,762 20, 2|, 22, 23,etc. from the base line and then threaded connection just described andto slide carriage 26 to any desired point over the face of chart I8 toalign the index line 25 with a desired mark or record on chart l8, forexample, base line l9, and then to engage the carriage 26 with thethreaded shaft 21 at that point by turning knob 43 to lower cams 4! fromtheir engagement with the bottom face of member 35. g

In operation, chart I8 is secured beneath clamp-- ing bars l6 and theentire chart holder H is adjusted by means of screw I 3 so'that baseline I9 is parallel to index 25 on cursor 24; Carriage 26 is thenmoved'so that index 25 is exactly aligned with base line l9 and thereset 34 of revolution counter 32 is turned so that all of dials 33indi- :'cate zero. Knob 43 is turned so that the upper member 35 ofcarriage 26 engages the threaded shaft 21. Carriage 26 is then movedacross the face of chart I 8 by rotating shaft 21, for example, v bymeans of the motion multiplying means 29.

When index 25 on cursor 24 is exactly aligned with steps 20 or 2| or '22or 23, etc., the causes of revolution counter 32will indicate the lineardistance through which the cursor hasfbeen moved, and if themathematical relationships of" threaded shaft 21, gears 30 and 3i andthe in:

ternal gearing of revolution counter ,32 have been properly chosen, thelinear distance will be exaccurate in operation and adapted to be usedcontinuously through a. working day with much less effort on the part ofthe operators than the previously used procedures ofjscaling thesedistances with steel, scalesusing magnifiers and the like, to obtainaccurate readings of the; linear distances involved. Although a s ingleexample of. means embodying this invention hasbeen illustrated anddescribed, itis obvious that numerous 'modifica-' tions and changes:could be made without depart-' ing from the invention-, and all suchmodifi'ca-I tions and changes that come within the scop of the appended.

I claim:

claim are embraced thereby; 1

Apparatus for measuring a succession of linear distances on a curve suchas a pressure-time chart, said curve having a succession Of CIitICHJpoints spaced at unknown distances'from a base line, comprising a base;pivoted means on'said base for holding said chart in a predeterminedaligned position, a movable cursor adapted to be positioned closelyadjacent. the surface of the chart and provided with an index to bealigned with critical markings thereon, a rotatable threaded haft onsaid base, a carriage threadedly mounted on said shaft and carrying saidcursor tomove the latter across said chart when said shaft is rotated,means on said carriage engaging said base to space said cursor abovesaid base and said chart, means on said carriage for selectivelyconnecting it to said threaded shaft, and

disconnecting it therefromQand arotation indicater for said shaft whichwill add to its total upon rotation in one direction and subtract'fromits total upon rotation in the opposite direction, so calibrated andarranged. that the linear distances of said critical points on saidchart will be accumulated on said rotation indicator during motion ofsaid cursor from said base line, and subtracted during motion of saidcursor toward said base line. I v HUGH B. WEBSTER.

